Locking arrangements for locking brake parts held under tension are known in practice and, in said locking arrangements, a first brake part has a tooth system, into which a catch provided on a second brake part engages by means of an engaging nose and thereby secures the two parts relative to one another in terms of rotary motion. By way of example, a locking arrangement of this kind is provided for locking the brake actuating lever on a lever holder or for locking a brake cable adjustment device when the brake actuating lever is raised and the free movement of the adjustment device is supposed to be blocked.
In known locking arrangements, there is a problem that, at certain lowering angles, an engaging nose shaped in the form of a tooth comes into contact with a tooth of the tooth system in such a way that the static friction is sufficient to achieve metastable retention of the catch provided with the engaging nose, but this is still not a positive-locking position of engagement between two tooth flanks of the tooth system. This metastable position, which is also referred to as “half locking”, may be overcome in the event of shocks or the like, with the possible result that the engaging nose enters the depression between two adjacent tooth flanks and reaches a stable locking position, there is, however, a risk that instead the engaging nose slides off and, under the tension of the brake cable, slides into the lowered brake position with the brake actuating lever, the result being that the parking brake is no longer secured. A metastable position is adopted especially when the tangents to those areas of the engaging nose and of the tooth of the tooth system which come into contact are approximately parallel.
DE 102 12 673 A1 shows a locking arrangement for locking a brake part which is held by the tension of a spring, is designed as a cable tensioning disk and is pivotable about a main axis, where a tooth system with a plurality of adjacent teeth is provided on the cable tensioning disk. For engagement in the tooth system of the cable tensioning disk, a catch that can be pivoted about a catch coupling is disposed pivotably on a brake actuating lever, said catch having, at an engagement end, an engaging nose biased in the direction toward the tooth system and comprising three teeth, which is designed in such a way that all three teeth of the engaging nose correspond, at uniform intervals to one another, with the tooth pitch of the tooth system and can engage fully in the tooth system. When the catch enters the tooth system, a first tooth of the catch engages in the tooth system first of all and, given contact with the tooth system, the catch should pivot into an engagement position in which all three teeth of the engaging nose engage in the tooth system. The disadvantage with the known locking arrangement is, on the one hand, the required play in the pivot of the catch, this being necessary in order initially to insert just one, first tooth. Owing to the equidistant tooth intervals, there is furthermore the risk that all the tooth tips of the teeth of the engaging nose will come into contact outside the recesses of the tooth system, thereby allowing the catch to slide off. An auxiliary nose spaced apart from the engaging nose is not shown.